Problematic Dipterous Leaf Miners on Bracken (Pteridium Aquilinum)

Newsletter 36 November 2019

Problematic dipterous leaf Chirosia flavipennis (156 records) miners on Bracken (Pteridium aquilinum):

(i) Chirosia histricina and Chirosia flavipennis (Diptera:Anthomyiidae):

Chirosia histricina (247 records)

Photo © Barry Warrington

It was these mines, in late October, of a Chirosia species that seemed to be PB has found the adults of both species on straightforward to identify, using the dates ranging from 27 May to 4 August and he findings of Griffiths (1982), as Chirosia states that ‘the flight periods of both species flavipennis. largely overlap, with C.histricina only a few weeks in advance. This forms very similar mines to that of Chirosia histricina on the same host, but The C.histricina data include leaf-mine Chirosia histricina apparently occurs observations which have been coming earlier in the year. into IRECORD in recent years, and which may therefore also include some

C.flavipennis.’ Griffiths’ findings were based on a small sample of these Anthomyiid flies in North The adults must be reared for a positive America but a different picture merged identification of either species but PB once Phil Brighton (Anthomyiid welcomes leaf mine records without Recording Scheme) was contacted. rearing - recording them just as Chirosia, as such records could still give significant The records of each species from the NBN information. atlas, including data from the Anthomyiid Reference: Griffiths, GCD (1982) - Flies of Recording Scheme, are as follows. the Nearctic Region (Anthomyiidae)

(ii) Phytoliriomyza hilarella and Heterarthrus aceris is now Phytoliriomyza pteridii (Diptera: Agromyzidae): renamed to Heterarthrus fiora Liston sp.n:

A recent paper reviewing the Heterarthrus species sawfly leaf miners found that leaf mines previously identified as Heterarthrus aceris were in fact a misidentification and should be renamed Heterarthrus fiora

Photo © Barry Warrington

A similar situation occurs with two agromyzid miners on Bracken – Phytoliriomyza hilarella and Phytoliriomyza pteridii, where both form very similar mines.

Can they be separated on phenology?

Barry Warrington (Agromyzidae Recording Scheme) says ‘In the national database, there are 6 records of pteridii (7 June - 14 July), whilst there are 25 records of hilarella (25 May - 25 Aug). All records are Photo © Rob Edmunds of adult material with only one been a reared specimen (of hilarella).’ The mines of H.fiora are edge mines of Sycamore (Acer pseudoplatanus) and the Again the flight periods (and presumably pupal disc detaches and falls to the the mines) overlap and again the adults ground before the leaf falls from the tree must be reared for a positive (as shown). identification of either species.

More details: Reference: Liston, A, Mutanen, M, Viitasaari (2019) - On the taxonomy of Agromyzidae Recording Scheme: [email protected] Heterarthrus (Hymenoptera, Tenthredinidae), with a review of the Anthomyiidae Recording Scheme: West Palaearctic species, Journal of [email protected] Hymenoptera Research, 72, 83-126

Caloptilia fidella (Lep:Gracillariinae) – soon to occur in the UK?

Caloptilia fidella is a bivoltine leaf miner of Hop (Humulus lupulus) which was first discovered in Belgium in 2009.

Will it soon be a leaf miner in the UK?

It forms distinctive mines with leaves showing both the small white initial triangular mine in a leaf axil (as shown, in transmitted light and surface view) and also subsequent three small leaf rolls formed at the leaf edge (as shown opposite, with the first leaf roll formed): Photo © Carina Van Steenwinkel

Pupation occurs in a white cocoon which is formed under the leaf (as shown, with exuviae).

Photo © Carina Van Steenwinkel

Photos © Carina Van Steenwinkel

The adult (below) emerged on 13.ix.2012 Pleuroptya ruralis (Lep: Crambidae) may from a mine collected at Meerhout, be a confusion species? Belgium, on 02.viii.2012.

These spinnings by Pleuroptya ruralis (23.ix.2019) superficially resemble those of Caloptilia fidella but are not fidella as:

 There is no central white initial triangular mine (which is always seen)  The leaf roll is too large, those of fidella are smaller

Photos © Carina Van Steenwinkel

Photos © Rob Edmunds

The mine of E.subbimaculella showing the slit in the lower epidermis: Distinguishing between the commoner Oak Ectoedemia species

There are four commoner Ectoedemia species on Oak in the UK – E.albifasciella, E.heringi, E.quinquella and E.subbimaculella.

Ectoedemia quinquella forms contorted gallery mines (as shown) whereas the Photo © Rob Edmunds other three ultimately form blotches, after an initial thin gallery. The larval head of E.subbimaculella is a dark blackish brown (as shown):

Photo © Rob Edmunds

Photo © Rob Edmunds Of the remaining three only E.subbimaculella forms a blotch with a slit These mines are found during October in the lower epidermis. With the others and November. the blotch remains intact. The remaining two blotch miners have different phenologies and larval characteristics, with E.albifasciella forming

mines August to October and E.heringi October to November.

The larva of E.heringi has a darker reddish The early instar larva of E.albifasciella brown head (as shown): showing some ventral plates:

Photo © Ben Smart Photo © Ben Smart

Whereas the larva of E.albifasciella has a E.heringi and E.subbimaculella do not very pale brown head (as shown): have these ventral plates.

Interestingly E.quinquella larvae have distinctive black ventral plates, from the second to early fourth instar.

The larva of E.quinquella showing black ventral plates:

The larvae can also be identified at an early stage by the presence of ventral plates, with only E.albifasciella having these in the early instars, but they are not Photo © Rob Edmunds very distinct.

The plates are thought to have a protective function and are lost by the final instar.

Reference: (ii) A Field Guide to the Smaller Moths of Great Britain and Keys to Nepticulid mines and larvae: Ireland: Johansson R, Nielsen ES, Nieukerken EJ van & Gustafsson B (1990)- The Nepticulidae and Opostegidae Lepidoptera) of North West Europe. – Fauna Entomologica Scandinavica 32.1 p77-98

Green Islands:

A very interesting blog summarising present knowledge on Green Island formation by Simon Leather: https://simonleather.wordpress.com/201 9/09/10/green-islands-mining-cytokinins/

Pocket Guides to leaf mines:

Some suggestions if you are looking for a guide to leaf miners that you can carry in the field. The following are all guides to lepidopteran miners (and I’ve been using this constantly over the microlepidoptera). past year (since publication) and cannot recommend it highly enough.

It is a paperback with a plastic cover (so

(i) Leafmine site keys: can be used in the field) and is packed full The guide produced by Barry of masses of useful information ranging Dickerson is very popular on leaf mine from phenology to distribution maps to excursions and prints out to a compact descriptions of the life stages. handy pocket size. An essential purchase for every http://leafmines.co.uk/html/Mine_Gui microlepidopterist! de.htm

(iii) Micro-moth Field Tips:

Another very useful field guide, with life stages beautifully photographed by Ben Smart.

Although the title refers to Lancashire and Cheshire it is applicable throughout the UK and contains many descriptions of leafminers on a month by month basis. There is generally one species described on each page, with summaries of other species to find at the end of each chapter.

My copy is very well used!